The present disclosure relates to semiconductor devices. Higher integration of semiconductor devices may be used to address consumer demand for superior performance and inexpensive prices. In the case of semiconductor memory devices, because their integration may be an important factor in determining product prices, increased integration may be especially beneficial. In the case of typical two-dimensional or planar semiconductor memory devices, because their integration is mainly determined by the area occupied by a unit memory cell, integration may be greatly influenced by the level of a fine pattern forming technology. However, the extremely expensive process equipment used to increase pattern fineness may set a practical limitation on increasing integration for two-dimensional or planar semiconductor memory devices.
To overcome such a limitation, three-dimensional memory devices (that is, including three-dimensionally arranged memory cells) have been proposed. In the case of a three-dimensional memory device, it may be beneficial to three-dimensionally arrange not only memory cells but also signal or interconnection lines (e.g., word lines or bit lines) providing access to the memory cells.